Control device for hoisting machines

ABSTRACT

For controlling the movements of the jibs of a first crane and at least a second crane mounted in opposed relation on fixed stands on each side of a handling area so that a load suspended from the two cranes maintains a constant predetermined orientation within said handling area irrespective of the swinging and steeve of the first crane. The device comprises a first movable arm connected to the jib of the first crane so as to reproduce the movements in swinging and steeve of the first crane, a second movable arm connected to the jib of the second crane and mechanically connected to the first arm in such manner as to effect movements corresponding to the position that the jib of the second crane must occupy in accordance with the position of the jib of the first crane given by the first arm.

'United States Patent 1191 Havard et al. Nov. 4, 1975 CONTROL DEVICE FOR HOISTING 3,489,293 1/1970 Sallow 212/39 R MACHINES [76] Inventors: Jean Havard, Avenue de Thalie, W' WWW-Frank Werner 44470 Carquefou; Henri Chamnnat Asszstant Exammer-I .awrence J. Oresky 95 Rue de la Galamiere 44400 Attorney, Agent, or FlrmHolman & Stern Reze; Francois Cova, Lotissement de Bel Air, 44 Carquefou, all of ABSTRACT France For controlling the movements of the jibs of a first [22 i 19 1973 crane and at least a second crane mounted in opposed relation on fixed stands on each side of a handling [21] APPL N05 426,043 area so that a load suspended from the two cranes maintains a constant predetermined orientation within [30] Foreign Application priority Data said handling area irrespective of the swinging and Dec. 19 1972 France 72 46115 steeve of the first crane. The device comprises a first Jul 31 1973 France 73'286o1 movable arm connected to the ]lb of the first crane so y as to reproduce the movements in swinging and steeve [52] U S Cl 47. 214/1 RCM of the first cran'e, a second movable arm connected to [51] Ilit. Cl. iiiiiiiiiiiiiiiiiiiiiiii B66C 23/00 the jib of the second crane and mechanically con- [58] Field 0f 58 R 59 R nected to the first arm in such manner as to effect R f 214/1 movements corresponding to the position that the ib of the secondcrane must occupy in accordance with [56] References Cited the position of' the jib of the first crane given by the first arm. UNITED STATES PATENTS gm 0 2,354,182 7/1944 Christoffersen 212/3 17 D'awmg Fgures U.S. Patent Nov. 4, 1975 Sheet 1 of 7 3,917,074

FIGJG US. Patent Nov. 4, 1975 Sheet 2 of7 3,917,074

US. Patent Nov. 4, 1975 Sheet 3 of7 3,917,074

FIG.6-

U.S. Patent Nov. 4, 1975 I Sheet4 of7 3,917,074

U.S. Patent NOV.4, 1975 Sheet5of7 3,917,074

US. Patent Nov. 4, 1975 Sheet 6 of7 3,917,074

=3. F up or U.S. Patent Nov. 4, 1975 Sheet 7 of7 CONTROL DEVICE FOR HOISTING MACHINES The present invention relates to the synchronization of the movement of two cranes mounted in opposed relation on each side of a handling area, as the hold of a ship. Each of these hoisting means has a jib which is movable about its post, mounted at a fixed station, in two directions of freedom apart from the hoisting of the suspension hook:

a. swinging about a vertical axis of the post;

b. steeving, that is to say, the mouvement of the jib in a vertical plane about a pivot having a horizontal pivot axis (luffing).

The device for synchronizing the movements of the present invention is in particular adapted to maintain a swing-bar (or the load) suspended from two crane hooks in a direction which is constantly parallel to a given axis (for example the axis of a ship) irrespective of the displacement of the package or load above the handling area. The two points of suspension always have the same height (swing-bar constantly horizontal) owing to the action of a known device synchronizing the hoistings with which device the present invention is not concerned.

It is known to equip each one of the two cranes, actuated together, with a calculation amplifier for imparting the necessary steeve angle. One of the hoisting machines also has another calculation amplifier for the swing mechanism so as to synchronize the latter with that of the other crane. The calculator determines mathematically the different command values or complementary command values applied to the steeving and swing mechanisms so as to preclude oblique pulling forces which adversely affect the stability of the cranes. Such a device therefore requires at least two complex and costly calculating units the reliability of which is ensured at the cost of many interventions and a constant maintenance. Moreover, the handling area is very limited with respect to the areas covered by the ends of the jibs.

It is essential to move the posts of the cranes if it is desired to serve other points of the loading area. The path of the packages is uniform for defined positions of the supports of the machines.

The control device according to the present invention avoids the aforementioned drawbacks. The crane posts remain at a fixed station, notwithstanding a notable increase in the area served under imposed conditions, that is to say, the maintenance of the swing-bar parallel to itself with the suspension hooks vertical. The path of the load may be varied without complicating the operations carried out by a single unskilled crane operator. Slow approach speeds can be obtained as desired by the operator. The maximum speeds of each of the cranes are automatically guaranteed by a safety device. The system determining the angles of steeve and swinging of the jibs is the same. It takes up a small amount of space, is compact and located within a frame sheltered from the surroundings. It is designed with mechanical parts which require no maintenance. It allows each crane to very easily resume its independence. Consequently, it allows very many advantageous coupling combinations between different cranes located at the end of, or between, successive handling areas.

The invention provides a device controlling the movement of the jibs of a first crane and at least a second crane mounted in opposed relation on fixed stands,

on each side of a handling area, so that a load suspended from the two cranes maintains a constant predetermined orientation within said handling area irrespective of the swinging and steeve of the first crane, termed the pilot crane, said device comprising a first movable arm coupled to the jib of the first crane so as to reproduce the movements of swinging and steeving of the first crane, a second movable arm coupled to the jib of the second crane, termed the follower crane, and operatively connected to the first arm so as to move in a way corresponding to the position that the jib of the second crane must occupy as a function of the position of the jib of the first crane which is given by the first arm.

Further features and advantages of the present invention will be apparent from the ensuing description with reference to'the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic elevational view of the two cranes;

FIG. 2 is adiagrammatic plan view of the two cranes;

FIG. 3 is a diagrammatic elevational view of one of the cranes with its device for effecting a horizontal displacement of the load irrespective of the steeve;

FIG. 4 is a vertical sectional assembly view of the mechanical syste'm controlling the pilot arm and follower arm which are oriented approximately in the same plane; v

FIG. 5 is adiagrammatic elevational view of the follower arm and pilot arm;

FIG. 5a is a diagrammatic plan view of the follower arm and pilot arm;

FIG. 6 is a sectional view, taken on line AA of FIG. 4, of a detail of a plate carrying the columns;

FIG. 7 is a detail view of a device effecting the swinging and steeving of the pilot arm;

FIG. 8 is a horizontal sectional view, taken on line CC of FIG. 4, of the follower and pilot arms;

FIG. 9 is a horizontal sectional view, taken on line DD of FIG. 4; of the control of the steeving of the pilot arm and the control of the steeving of the follower crane by the follower arm;

FIG. 10 is a -diag'rammatic plan view of the handling area;

FIG. 11 is a diagram of the control of the cranes through the steeving of the pilot and follower arms;

FIG. 12 is a-plan view of another embodiment of the mechanical device according to the invention for determining the orientations;

FIG. 13 is a diagrammatic plan view of the arms;

FIG. 14 is aplan view of the same device with the arms inclined;

FIG. 15 is an elevational view of the same device, and

FIG. 16 is a sectional view taken on line AA of FIG. 15.

FIG. 1 shows diagrammatically two cranes G1 and G2 at a fixed station. The first crane is termed a pilot crane and it is only this crane which is operated by the crane operator. The second crane, which is termed a follower crane, is operated automatically by the device according to the invention. The two hoisting machines are located on each side of, for example, the hold 4 of a ship. The pilot crane G1 pivots about a vertical axis xx of its post. Its jib is raised and lowered about a point 5 located approximately on the axis x-x. The same is true of the follower crane G2. The two jibs are in opposed relation. Their swingings a1 and a2 (FIG.

2) are in conjugate relation and vary on each side of the straight line 5-6 which interconnects the pivot centres. At any moment said swingings are such that the vertical projections 7 and 8 of the ends 9 and 10 of the jibs 11 and 12 of the cranes remain at a constant distance apart d, the straight line 78 always being parallel to the line 5-6. To obtain this result, irrespective of the swinging a1 and the steeve Bl imposed by the pilot crane 1, the follower crane 2 will receive the command to assume an swinging a2 and a steeve B2. In fact, the jibs usually cannot descend below the positions 11a and 12a. The steeve angles are therefore counted generally according to 3'1 and 5'2 (FIG. 1). The straight line 7-8 is embodied either by a swing-bar 13 or by any load, either one being suspended at two points 14 and 15.

When each of the jibs is raised, the swing-bar moves horizontally when the cable winder 16 is stationary. This is obtained owing to a given geometry of the position of the pulleys, such as those shown in FIG. 3. This known system will not be described here. It will merely be mentioned that, in the raised position, an automatic correction, acting on the rotation of the winch or winder 16, compensates for certain variations in height of the point 14. The swingb ar 13 may thus always move parallel to itself in a zone 17 shown in FIG. 10. The device according to the invention is enclosed in a frame 18 (FIG. 4) mounted in the cabin 3 of the pilot crane 1. The frame comprises a sealed cover 19 and base plate 20. It is integral with the post 21 of the crane G1 and pivots on its fixed stand about the axis 22. It therefore rotates in absolute movement about the latter. It is secured in position by columns 23 mounted on a plate 24 which is integral with the post 21 through two assembled rings 25 and 26. Engaged between the two rings 25 and 26 is a flange 27 which is fixed, it being integral with the tube 28 wich is part of the fixed stand of the crane G1. Extending through the tube 28 are electric cables 29 which interconnect the two hoisting machines (pilot and follower) and lead to rotating contacts 30. These connections correspond to the part indicated L in the electric circuit diagram shown in FIG. 11 which will be described hereinafter. The rings 25 and 26 therefore pivot about the flange 27. Another flange 31 is disposed between the flange 27 and the ring 25 and it is slidably mounted on a shaft 32 but drives the latter through a sliding key 33. It may be connected to the ring 25 or to the flange 27 by the action of an electromagnet 34. The contacting surfaces are provided with friction washers so that it is possible, as desired, to drive the flange 31 with the pivoting post 21 (through the ring 25) or hold it stationary (through the flange '27). This assembly therefore constitutes a remote controlled clutch of the shaft 32. When the latter is held stationary on the flange 27, the frame 18 rotates with respect to the shaft 35, which becomes stationary, the shaft 35 extending through the bottom 20 of this frame through a sealed rolling bearing 36. The coaxial shafts 35 and 32 are interconnected by two cranks 37 and 38 and a column 39. The shaft 35 is fixed rigidly in its upper part to a member 40 which is, in this case, stationary with respect to the frame 18. FIG. 7 is a sec tional view of this detail to an enlarged scale. The member 40 carries a horizontal shaft 41 to which is fixed an arm 42, termed the pilot arm of the mechanical control device. The movement of the stand with respect to the pilot arm 42 represents, in the opposite direction, the variable swinging of the jib with respect to the ground.

The steeving movement of the pilot arm 42 is achieved by means of a sleeve 43 provided at each end with a circular rack 44, the sleeve being slidable on the shaft 35 under the effect ofa pinion 45 which is meshed.

with the rack. The pinion 45 is mounted on a shaft 46 disposed in a member 47 integral with the frame. The shaft 46 is connected by a linkage to move with the steeving movement of the pilot crane. FIG. 7 shows that the pinions 45 and 48 rotate in synchronism and cause the pilot arm 42 to descend or rise in a manner identical to that of the pilot jib. The drive for the shaft 46 is shown in FIG. 9. An extension 46a of the shaft is freely mounted in a plate 49 integral with the frame. A flange 50 slidably keyed on the extension 46a affords either a drive through the flange 51 (rotating in accordance with the steeving of the crane) or a locking on the plate 49. Each alternative operation is rendered possible by an electromagnet 52 constituting the control of the clutch. The arrangement is similar to that previously described for the orientation movement take off. However, in the case where flange 51 and flange 50 are associated, the linkage (diagrammatically shown at 53) which interconnects the flange 51 and the 1 pilot jib is mounted in such manner that the rotation of the shaft 46 will be exactly the same and in the same direction as that of the pivot of the jib on the post of the pilot crane. The sleeve of the arm 42 will therefore be equal to that of the pilot jib.

With reference to FIG. 4, the pilot arm 42 terminates in a pivotal connection 54 to a slide 55 which moves freely without play on one of two vertical guides 56 and 57. The slide has a depending portion in which is formed the bore for the pivot pin of the arm. The dimensionj (FIGS. 4 and 8) is determined in the manner indicated hereinafter. The sleeve slides on the cylindrical guide through balls. The two vertical guides are mounted in a plate 58 constituting a carriage which moves in the manner of a small travelling crane. The plate 58 is slidable in a beam 59 which moves parallel to itself in the two slideways 60 mounted on the opposed faces of the frame 18. FIG. 6 shows a crosssectional view of this system for shifting the carriage 58 on which are fixed two additional reinforcements 57aand 57b. The plate 58 therefore moves horizontally in any direction while maintaining the axes of the cylindrical guides 56 and 57 vertical in a plane constantly parallel to itself. The pilot arm 42 imposes by its relative steeve and swinging (with respect to the frame) a well-defined position on the plate 58 through the slide 55. The latter is at any height on its guide 56. The other guide 57 is also provided with another slide 61 similar to the slide 56 and pivoted at 62 to a second moving arm 63 termed the follower arm. The latter therefore follows the movements of the pilot arm with different arm 63 is transmitted to the shaft 67 through the same device as that of the previously described pilot arm (pinions and circular rack slidable on the vertical shaft 68). The rotation of the shaft 67 controls the raising or lowering of the follower crane jib until the imposed steeve angle B2 is reached. The movement is transmitted through the shaft 69 connected to a potentiometer 70 (FIG. 9). The latter constitutes one of the parts of the motorized control of the steeving of the follower crane. Likewise, the shaft 68 (FIG. 4) drives a potentiometer 71 which participates in the motorized .control of the position of the follower crane, as concerns swing- In the arrangement described hereinbefore and diagrammatically shown in FIGS. 5 and 5a (views in elevation and plan), it will be considered that the segment PS represents the distance between the centres of the movements of the cranes (referencenumerals 5 and 6 in FIGS. 1 and 2). The two imaginary arms (PT)'and 73 (SV) obtained in accordance with the diagram of FIG. 5, are constantly parallel and equal to the pilot arm 42 and follo'wer arm 63. The steeving and swinging are therefore the same for 42 and 72 and for 63 and 73. The distance between the horizontal projections of the heads T and V of the imaginary arms is constantly equal to d (distance between the guides 56 and 57). It will be understood that all the arm lengths are representations, to the same scale, of the jib lengths. Thus the results aimed at by the present invention are achieved in so much as:

a. The distances f and j are'equaL'The shape of the ears integral with the slides is designed accordingly. A slight difference could however be allowed without marked effect on the desired result.

b. The crane jibs and the arms 42 and tively the same steeve.

c. The crane jibs have respective swingings which are inverted with respect to those of the arms 42 and 63. The inversion exists by symmetry with respect to the line PS (FIG. 5a). Itis very easy to embody and reestablish in the controlsystem. The swingings of the arms are counted in relative value with respect to the bottom 20 of the frame.

In order that the conditions (b).and (c) be satisfied, the position controls mustbe well conjugated, .with the appropriate corrections.- FIG. 11 shows by way of example a diagram comprising, in the centre part, a diagrammatic representation of the pilot arm 42 and its drive by the crane parts through clutches 34 and 52. In contradistinction to the other Figures, the follower arm 63 is on the left side, the pilot arm being on the right side. The pilot arm has two detecting potentiometers (steeve 74,, swinging 75). The follower .arm furnishes, through its steeve potentiometer 70 and its swinging 63 have r'especpotentiometer 71, the data which will be compared at 76 and 77 with those which come from the potentiometers 78 and79 connected to-the corresponding servomechanisms. At 80 and 81 there is provided a motorization controlled by an information of the speed of displacement of the jib in swinging and steeving. At 82 and 83 there'may be included a ramp (or cam) giving progressive movements. As soon as the speed of either of the movements increases abnormally on the follower crane (pilot crane raised suddenly to the upper position for example), a signal is produced by 84 well before the maximum limit speed is reached, determined by the potentiom'eter P acting as a reference uhe elements E are comparators whose output state depends on the direction or sense of the difference between the voltages a: and speed reference V An order to slow down is then given to one or the other of the mechanisms of the pilot crane at 85 or 85a. This order is superimposed on that already given by the control lever 86 or the like common to the gyration (swinging) and steeving for the two opposed cranes. Thyristor drive devices are mounted at 87 and 88. Ramps which soften the the operations are mounted at 89 and 90.

The hoisting of the hooks is also synchronized by means of the same hoisting lever 91 or the like through ramps and thyristor drive devices 92 and 93. Further, at 94, a corrector of the horizontality of the movement of the load acts when the steeve angle is high (jib approaching the vertical).

For given jib lengths, it should be mentioned that for a given and. fixed distance between the cranes, it is sufficient to change the plate carrying the guides 55 and 57 (distance d) when a swing-bar of different length is employed. Moreover,- if the crane jib or jibs are changed, the arm or arms of ,the device may be replaced by levers of proportional length.

By acting on the electromagnets 34 and 52 of the clutches on the transmissions of movement of swinging and steeving in the cabin of the pilot crane, it is possible to render the two arms of the device according to the invention stationary with respect to .the frame 18. The pilot crane can then move alone while the other crane remains stationary.

The unit which has just been described is simple and may be operated by an unskilled crane operator. The handling area is easily covered and maintenance is reduced.

But the mechanical clearances, which must be very small, require a very careful and difficult-construction. Jamming phenomena occur between the pilot and follower arms and require sliding assemblies which are carefully designed with special parts which are delicate to assemble and are unsuitable for mass-production or repeated production. Moreover, such an arrangement implies that the mechanical synchronizing device (the driving of the pilot arm by the pilot crane) be mounted in the post of the pilot crane in the vicinity of its steevingfand swing mechanisms. This can be a drawback in the desire to reduce the overall size and facilitate access.

The embodiment which will now be described with reference to FIGS. 12 to 16 avoids the aforementioned drawbacks. It precludes the jamming between the pilot and follower arms by employing a mechanical system which concerns only the horizontal projections of the crane jibs, that is to say, the orientations. The play or clearance is easily suppressed by simple play-taking up systems. The indications of the steeve angles or the indications of the lengths of the horizontal projections of the jibs, are automatically afforded by the value of the cosine ofB and [3 which are easy to calculate. Indeed, the ratio length of the projection/length of the jib always gives the value of cos B and therefore B2; Similarly; the value of [3, gives constantly the length of the horizontal projection of the jib. Consequently, the two corresponding units of calculation are very small. They are currently available from industry. In other words, a large part of the complex systems for mathematical solutions is replaced by a simple mechanical device while maintaining two elementary units of calculation which avoid the kinematic complications of an entirely mechanical solution.

There result" a reduction in cost and a reduction in the overall size. The suppression of play and the limitation of the lack of precision of a fully electronic system (in particular as concerns the response time) result in an improvement in overall precision.

To describe this device, reference will be made to FIGS. 12, 14, and 16. The fixed parts of this mechanism are constituted by two rings 101 and 102 shown in FIGS. 15 and 16 and interconnected by a strut 103 which determines the value of their centre distance E. This assembly is completed by legs 104 which are sufficiently spaced apart and reinforced by connecting members 105 so that the support thus formed is stable and rigid. This support carries two tables 106 and 107 which are braced at 108 and on which a motor 109 with its gear wheel 110 is secured. The rotation of the shaft of the motor and consequently the shaft 111 of the device is so controlled that it exactly reproduces (modifled by the gear ratios) the angular movements of the swinging shaft of the pilot crane. In other words, the shaft 111 of the device is electrically synchronized in a precise manner with the swinging shaft M1 of the pilot crane G1 (FIG. 1). Between the latter (M1) and the motor 109 there are disposed all the necessary electrical means including power amplifiers. For example, according to a known method, the angular deviations of the shaft of the motor 109 and the swinging shaft of the pilot crane G1 are constantly compared by means of the indications of the two rotary potentiometers (109a for the motor 109). The electrical circuit is sufficiently conventional and need not be shown in the drawing.

Each of the rings 101 and 102 carries two bearings in which is journalled the vertical shaft 111 in respect of the first ring, and a shaft 112 in respect of the second ring. The ring 111 carries in its lower part a gear wheel 113 which is driven by the gear wheel 110 of the motor 109. Consequently, if the gear ratio between the gears 110 and 113 is correctly chosen, the vertical shaft 111 rotates about its axis ab in the same way as that which controls the swinging of the pilot crane about the axis x-x'. Fixed to the upper part of the shaft 111 and locked in position is a horizontal movable table 114 which rotates with this shaft. Placed on this table there is a ball bearing slide which comprises a fixed part 115 screwthreadedly engaged with the table 114 and a movable rule 116. The latter carries a rack 117 with which engages a pinion 118 mounted on the shaft 119 of a motor 120. The latter is secured by a support 121 to the table 114 which is movable about the axis ab. A rotary potentiometer 122, driven by the shaft 119, is secured to another support 123 integral with the table 114. The potentiometer 122 operates in the manner described hereinafter. The assembly just described is therefore pivotable with the table 114 about the vertical axis ab. It follows the movements of swinging of the pilot crane G1.

The rotation of the shaft of the motor 120 (not shown in FIG. 15) and therefore of the gear pinion 118 is directly proportional to the cosine of the steeve angle )3, of the pilot crane G1 and therefore to the dimension K1 (horizontal projection of the jib of the pilot crane G1) indicated in FIG. 2. This relation between the angle 3,, easy to detect on the crane G1, and the rotation of the motor 120, is given by a conventional resolver which converts values of angle into cosine values, the latter being converted into a voltage which is permanently compared with that which is furnished by the potentiometer 122 (coupled at 120). This conventional arrangement is not shown in the drawing. Let 0 be a point located at the end of the rule 116 and a the point of the pivoting of the rule while sliding. The origin of the movement and the reducing ratios are such that K1 and k1 (FIGS. 12 and 14) remain constantly proportional; Kl n.kl.

An assembly of identical parts is mounted on the upper part of the shaft 112 and pivots about the vertical axis cd (FIG. 15). The horizontal table 124 carries a slide (part 125 screwed to the table and movable rule 126). The rack 127 secured to the rule 126 engages the gear pinion 128 which it drives. Mounted on the shaft 129 of the pinion 128 is a rotary potentiometer 130 (shown in dot-dash line in FIG. 16) fixed to the table 124 by a support 124a. This potentiometer, which also acts as a bearing for the shaft 129, furnishes to the motor R2 for steeving the follower crane (through a device described hereinafter) the information concerning the displacement of the rack 127 and therefore of the rule 126. The latter is drigen by the other rule 116 through a vertical pivot pin 131 having an axis 00 and extending through two overlapping end portions of the rules 116 and 126. FIG. 14 shows how the rules move in the same horizontal plane, the rule 116 shifting the other rule 126.

It will be understood that the table 124 which supports the rule 126 must rotate freely about the axis cd in order to follow the rotation a, of the rule 116 about the axis ab. Its rotation on: is recorded by the rotary potentiometer 132 driven by the vertical shaft 1 12. A gear wheel 133 on the shaft of the potentiometer 132 meshed with a gear wheel 134 ensures this drive. The potentiometer is fixed on the strut 103 by the columns 135 and a plate 136. It transmits the information concerning the value of oz; of swinging which the follower crane G2 must have and controls the motor M2 of the latter about its axis y y.

It will be observed that under these conditions diagrammatically represented in FIGS. 13 and 2:

the variable distance a0 (dimensionkl) is proportional to K1 LI cos [3, (horizontal projection of the jib L1 of the pilot crane). Whence Kl n.kl (n conim) the distance as (dimension k2) is proportional to K2 (horizontal projection of the jib L2 of the follower crane). K2 n.k2 (n=constant) As K2 L2 cos {3 (L2 constant) it is deduced that cos [3 (n/L2).k2 (n/L2 =constant). Knowing the dimension k2 from the poten-* tiometer 130 determining the displacement of the rule 126 with its rack 127, it is easy to calculate the value of cos. B and therefore the value of [3,. This is carried out by a conventional resolver which converts the cosine values into angle values with a correcting coefficient n/L2. This resolver is not shown in the drawings as it is of conventional construction. Its information controls, through an amplifier, the motor R2 for steeving the follower crane through an electric circuit which is also conventional;

the length d of the swing-bar 113 in no way intervenes in the operation of this type of synchronism;

the length of the jibs of the cranes may be different;

the follower crand jib is consequently perfectly controlled, for steeving and swinging, by the movements of the pilot crane.

The potentiometer 122 may be chosen with a ratio 3 in order to increase the fineness of the information. Thus, when the motor 120 rotates one revolution, the

potentiometer effects three revolutions. The rotation of the other potentiometers may also be muliplied.

In order to improve still more the precision, one or more systems for taking up play may be employed in the drives through gear pinions and gear wheels. For example, in the arrangement shown in FIG. 15, the support 136 of the gear pinion 133 connected to the potentiometer 132 is pivoted to the column 135. A spring 137 biases the gear pinion 133 on the ring gear 134 and suppresses the play between the gear teeth.

Mounted at the lower part of the vertical shaft 111 is a cam 138 (FIG. 16) which actuates two electric switches 139 and 140 provided with rollers. These contacts limit the extreme positions of the pivotable table 114 driven by the motor 109. The table 114 carries laterally the two supports 141 and 142 of two microcontacts 143 and 144 whose action on abutments 145 and 146 mounted at the ends of the sliding rule 1 16 limits the travel of the latter. One of the microcontacts causes the slowing down and the other causes the stoppage. The same is true in respect of the other sliding rule 126 which carries abutments 147 and 148 acting on contacts 149 and 150. The microcontact 151 in cooperation with the abutment 152 (fixed to the rule 126) stops the sliding in the other direction. Any other safety device may be mounted for limiting the movements. The cross-hatched region in FIG. 14 shows the area which may be covered by the pivot pin 131.

By way of a modification, the fixed strut 103 may be constituted by two sliding parts so as to be adaptable to different centre distances between the cranes. It must be understood that the invention is not intended to be limited to the embodiments of each one of the parts of the device as the invention embraces all possible modifications within the scope of the following claims.

Having now described our invention what we claim is new and desire to secure by Letters Patents is:

1. A device for controlling the movements of a jib of a first crane, termed a pilot crane, and a jib of at least a second crane mounted in opposed relation on fixed stands on opposite sides of a handling area, said device comprising a first movable arm connected to the jib of the first crane so as to give an indication relative to the movements in swinging and steeve of the first crane, a second movable arm connected to the jib of the second crane, termed follower crane, and means for operatively connecting the second arm to the first arm in such manner that the second arm effects movements corresponding to the position that the jib of the second crane must occupy in accordance with the position of the first crane given by the first arm whereby the load being hanld d by said cranes always remains parallel to a predetermined orientation irrespective of the orientation and steeve given to said pilot crane.

2. A device as claimed in claim 1, comprising a post for each crane, a frame integral with the post of the first crane, the first arm being able to be swung and raised in the frame, the second arm also being able to be swung and raised in the frame, said connecting means between the first arm and second arm comprising two vertical guides which are parallel and mounted at a constant distance from each other, two pivotal slides respectively slidably mounted on the guides, the first arm and second arm having free end portions respectively pivoted to the slides.

3. A device as claimed in claim 2, comprising two vertical opposed walls of the frame, two slideways fixed to the two opposed walls, a beam slidable on the slideway, and a carriage slidable on the beam and carrying the vertical guides.

4. A device as claimed in claim 2, wherein each of the pivotal slides comprises a horizontal pivot pin which is at a distance from the axis of the corresponding vertical guide which is equal to the distance between the vertical axis of swinging of the first arm and a horizontal shaft carrying the first arm.

5. A'device as claimed in claim 1, wherein the post of the first crane is mounted to rotate on the corresponding fixed stand about an axis and the axis of swinging of the first arm is aligned with the axis of rotation of the post on its stand.

6. A device as claimed in claim 1, comprising an electromagnetic brake for limiting the swinging of the first arm with respect to the frame by rendering the first arm stationary with respect to the stand of the first crane.

7. A device as claimed in claim 6, comprising a first shaft which extends into the frame and is operatively connected to an element of the electromagnetic brake, a member fixed to the end of the first shaft, and a horizontal shaft rotatably mounted in the member, the first arm being fixed to the horizontal shaft.

8. A device as claimed in claim 6, further comprising a shaft for swinging the first arm, a clutch associated with the electromagnetic brake and adapted to render the shaft swinging the first arm integral with the frame so as to render the first arm stationary with respect to the frame.

9. A device as claimed in claim 1, further comprising means for steeving the first arm with respect to the frame, said steeving means comprising a linkage connected to be actuated by the jib of the first crane, a member integral with the frame, a horizontal shaft extending through the wall of the frame and being rotatable in the member, a first gear pinion carried at an end of the horizontal shaft, a first circular rack, an orienting shaft for the first arm, a sleeve slidably mounted on the orienting shaft, a first circular rack provided at an end of the sleeve and meshed with the first gear pinion, a second circular rack at an end of the sleeve, a shaft carrying the first arm, a second gear pinion mounted on an end of the shaft carrying the first arm and meshed with the second circular rack.

10. A device .as claimed in claim 9, further comprising means for-de-clutching and immobilizing the means for steeving the first arm, said de-clutching and immobilizing means being arranged outside said frame.

11. A device as claimed in claim 1, comprising a first servomechanism for steeving the jib of the second crane, a second servomechanism for orienting the jib of the second crane, a horizontal shaft for controlling the first servomechanism, a vertical shaft for controlling the second servomechanism, the second arm being mounted in the frame in the same way as the first arm, the steeving of the second arm being transmitted to the horizontal shaft, and the swinging of the second arm being transmitted to the vertical shaft.

12. A device as claimed in claim 11, wherein the first and second servomechanisms comprise means for automatically limiting the speed of displacement of the jib of the first crane as soon as the speed of displacement of the jib of the second crane reaches a maximum limit value.

13. A device for controlling the movements of a jib of a first crane and a jib of at least a second crane mounted in opposed relation on fixed stands on opposite sides of a handling area so that a load suspended from the two cranes maintains a constant predetermined orientation within said handling area irrespective of the orientation and steeve given to the first crane, termed the pilot crane, said device comprising a first movable arm connected to the jib of the first crane so as to reproduce the movements in swinging and steeve of the first crane, a second movable arm connected to the jib of the second crane, termed follower crane, and means for operatively connecting the second arm to the first arm in such manner that the second arm effects movements corresponding to the position that the jib of the second crane must occupy in accordance with the position of the first crane given by the first arm, the first and second movable arms being constituted by a first rule and a second rule, there being provided a first table and a second table which are horizontal and mounted to rotate about a vertical axis, two slideways which are respectively integral with the two tables in which slideways the two rules are respectively slidable, the axis of sliding of each rule intersecting the axis of rotation of the corresponding table, and a vertical pivot pin which embodies ends of the horizontal projections of the jibs of the first and second cranes and interconnects ends of the rules located between the axes of rotation of the tables.

14. A device as claimed in claim 13, comprising a controlled electric motor having an output shaft for reproducing angular swinging movements of the first crane, the first table having a shaft which defines the axis of rotation of the first table and is connected to said output shaft through a set of gears.

15. A device as claimed in claim 14, comprising means for synchronizing said output shaft with a motor having an output shaft for swinging the first crane.

16. A device as claimed in claim 15, wherein said synchronizing means comprise two rotary potentiometers, each potentiometer being connected to the corresponding output shaft.

17. A device as claimed in claim 13, comprising a rotary potentiometer, an electric motor having an output shaft for driving the potentiometer, a gear pinion mounted on the output shaft, a rack provided on the first rule and meshed with the gear pinion, an electric motor for steeving the jib of the first crane and electrically connected to the last-mentioned motor.

18. A device as claimed in claim 17, comprising a resolver for rendering the rotation of the motor driving the first rack associated with the first rule directly proportional to the cosine of the steeve angle of the jib of the first crane, the resolver ensuring the conversion of the value of the steeve angle into its cosine value which is converted into a voltage which is permanently compared with the voltage of the potentiometer connected to the motor driving the first rack, the rotation of the motor connected to the first rack varying the values of the horizontal projections of the jib of the first and second cranes embodied by the distances between the pivot pin and the axes of rotation of the first and second tables.

19. A device as claimed in claim 18, wherein the second rule which is slidably mounted on the second table operatively connected to the mechanism for displacing the jib of the second crane comprises a second rack, there being provided a rotary potentiometer for furnishing information relating to the displacement of the second rack to a motor for steeving the second crane, and a gear pinion for transmitting the movement of the second rack to the last-mentioned potentiometer.

20. A device as claimed in claim 13, comprising a shaft for rotating with the second table, a set of gears, a rotary potentiometer having an actuating shaft which is connected to the shaft for rotating the second table, a motor for controlling the swinging of the second crane and electrically connected to the last-mentioned potentiometer.

21. A device as claimed in claim 13, comprising adjacent a free end of each rule two end-of-travel abutmerits, and microcontacts co-operative with the two abutments for limiting the travel of the corresponding rule, one of the microcontacts being for causing the slowing down and the other the stoppage of the corresponding rule.

22. A device as claimed in claim 13, wherein the second rule comprises a third abutment disposed in the vicinity of the pivot pin, there being provided a microcontact co-operative with the third abutment for stopping the translation of the rules.

23. A device as claimed in claim 13, comprising a shaft for rotating with the first table, a cam mounted on the shaft, two switches having rollers'for limiting the rotation of the first table at two extreme positions and being co-operative with the cam.

24. A device as claimed in claim 1, there being more than two cranes, the cranes to be controlled having jibs of equal lengths and being placed at equal distances from the first crane. 

1. A device for controlling the movements of a jib of a first crane, termed a pilot crane, and a jib of at least a second crane mouNted in opposed relation on fixed stands on opposite sides of a handling area, said device comprising a first movable arm connected to the jib of the first crane so as to give an indication relative to the movements in swinging and steeve of the first crane, a second movable arm connected to the jib of the second crane, termed follower crane, and means for operatively connecting the second arm to the first arm in such manner that the second arm effects movements corresponding to the position that the jib of the second crane must occupy in accordance with the position of the first crane given by the first arm whereby the load being hanlded by said cranes always remains parallel to a predetermined orientation irrespective of the orientation and steeve given to said pilot crane.
 2. A device as claimed in claim 1, comprising a post for each crane, a frame integral with the post of the first crane, the first arm being able to be swung and raised in the frame, the second arm also being able to be swung and raised in the frame, said connecting means between the first arm and second arm comprising two vertical guides which are parallel and mounted at a constant distance from each other, two pivotal slides respectively slidably mounted on the guides, the first arm and second arm having free end portions respectively pivoted to the slides.
 3. A device as claimed in claim 2, comprising two vertical opposed walls of the frame, two slideways fixed to the two opposed walls, a beam slidable on the slideway, and a carriage slidable on the beam and carrying the vertical guides.
 4. A device as claimed in claim 2, wherein each of the pivotal slides comprises a horizontal pivot pin which is at a distance from the axis of the corresponding vertical guide which is equal to the distance between the vertical axis of swinging of the first arm and a horizontal shaft carrying the first arm.
 5. A device as claimed in claim 1, wherein the post of the first crane is mounted to rotate on the corresponding fixed stand about an axis and the axis of swinging of the first arm is aligned with the axis of rotation of the post on its stand.
 6. A device as claimed in claim 1, comprising an electromagnetic brake for limiting the swinging of the first arm with respect to the frame by rendering the first arm stationary with respect to the stand of the first crane.
 7. A device as claimed in claim 6, comprising a first shaft which extends into the frame and is operatively connected to an element of the electromagnetic brake, a member fixed to the end of the first shaft, and a horizontal shaft rotatably mounted in the member, the first arm being fixed to the horizontal shaft.
 8. A device as claimed in claim 6, further comprising a shaft for swinging the first arm, a clutch associated with the electromagnetic brake and adapted to render the shaft swinging the first arm integral with the frame so as to render the first arm stationary with respect to the frame.
 9. A device as claimed in claim 1, further comprising means for steeving the first arm with respect to the frame, said steeving means comprising a linkage connected to be actuated by the jib of the first crane, a member integral with the frame, a horizontal shaft extending through the wall of the frame and being rotatable in the member, a first gear pinion carried at an end of the horizontal shaft, a first circular rack, an orienting shaft for the first arm, a sleeve slidably mounted on the orienting shaft, a first circular rack provided at an end of the sleeve and meshed with the first gear pinion, a second circular rack at an end of the sleeve, a shaft carrying the first arm, a second gear pinion mounted on an end of the shaft carrying the first arm and meshed with the second circular rack.
 10. A device as claimed in claim 9, further comprising means for de-clutching and immobilizing the means for steeving the first arm, said de-clutching and immobilizing means being arranged outside said frame.
 11. A device as claimed in claiM 1, comprising a first servomechanism for steeving the jib of the second crane, a second servomechanism for orienting the jib of the second crane, a horizontal shaft for controlling the first servomechanism, a vertical shaft for controlling the second servomechanism, the second arm being mounted in the frame in the same way as the first arm, the steeving of the second arm being transmitted to the horizontal shaft, and the swinging of the second arm being transmitted to the vertical shaft.
 12. A device as claimed in claim 11, wherein the first and second servomechanisms comprise means for automatically limiting the speed of displacement of the jib of the first crane as soon as the speed of displacement of the jib of the second crane reaches a maximum limit value.
 13. A device for controlling the movements of a jib of a first crane and a jib of at least a second crane mounted in opposed relation on fixed stands on opposite sides of a handling area so that a load suspended from the two cranes maintains a constant predetermined orientation within said handling area irrespective of the orientation and steeve given to the first crane, termed the pilot crane, said device comprising a first movable arm connected to the jib of the first crane so as to reproduce the movements in swinging and steeve of the first crane, a second movable arm connected to the jib of the second crane, termed follower crane, and means for operatively connecting the second arm to the first arm in such manner that the second arm effects movements corresponding to the position that the jib of the second crane must occupy in accordance with the position of the first crane given by the first arm, the first and second movable arms being constituted by a first rule and a second rule, there being provided a first table and a second table which are horizontal and mounted to rotate about a vertical axis, two slideways which are respectively integral with the two tables in which slideways the two rules are respectively slidable, the axis of sliding of each rule intersecting the axis of rotation of the corresponding table, and a vertical pivot pin which embodies ends of the horizontal projections of the jibs of the first and second cranes and interconnects ends of the rules located between the axes of rotation of the tables.
 14. A device as claimed in claim 13, comprising a controlled electric motor having an output shaft for reproducing angular swinging movements of the first crane, the first table having a shaft which defines the axis of rotation of the first table and is connected to said output shaft through a set of gears.
 15. A device as claimed in claim 14, comprising means for synchronizing said output shaft with a motor having an output shaft for swinging the first crane.
 16. A device as claimed in claim 15, wherein said synchronizing means comprise two rotary potentiometers, each potentiometer being connected to the corresponding output shaft.
 17. A device as claimed in claim 13, comprising a rotary potentiometer, an electric motor having an output shaft for driving the potentiometer, a gear pinion mounted on the output shaft, a rack provided on the first rule and meshed with the gear pinion, an electric motor for steeving the jib of the first crane and electrically connected to the last-mentioned motor.
 18. A device as claimed in claim 17, comprising a resolver for rendering the rotation of the motor driving the first rack associated with the first rule directly proportional to the cosine of the steeve angle of the jib of the first crane, the resolver ensuring the conversion of the value of the steeve angle into its cosine value which is converted into a voltage which is permanently compared with the voltage of the potentiometer connected to the motor driving the first rack, the rotation of the motor connected to the first rack varying the values of the horizontal projections of the jib of the first and second cranes embodied by the distances between the pivot pin and the axes of rotation of the first and second tables.
 19. A device as claimed in claim 18, wherein the second rule which is slidably mounted on the second table operatively connected to the mechanism for displacing the jib of the second crane comprises a second rack, there being provided a rotary potentiometer for furnishing information relating to the displacement of the second rack to a motor for steeving the second crane, and a gear pinion for transmitting the movement of the second rack to the last-mentioned potentiometer.
 20. A device as claimed in claim 13, comprising a shaft for rotating with the second table, a set of gears, a rotary potentiometer having an actuating shaft which is connected to the shaft for rotating the second table, a motor for controlling the swinging of the second crane and electrically connected to the last-mentioned potentiometer.
 21. A device as claimed in claim 13, comprising adjacent a free end of each rule two end-of-travel abutments, and microcontacts co-operative with the two abutments for limiting the travel of the corresponding rule, one of the microcontacts being for causing the slowing down and the other the stoppage of the corresponding rule.
 22. A device as claimed in claim 13, wherein the second rule comprises a third abutment disposed in the vicinity of the pivot pin, there being provided a microcontact co-operative with the third abutment for stopping the translation of the rules.
 23. A device as claimed in claim 13, comprising a shaft for rotating with the first table, a cam mounted on the shaft, two switches having rollers for limiting the rotation of the first table at two extreme positions and being co-operative with the cam.
 24. A device as claimed in claim 1, there being more than two cranes, the cranes to be controlled having jibs of equal lengths and being placed at equal distances from the first crane. 